From The Collaborative International Dictionary of English v.0.48:
Ditto \Dit"to\, adv.
As before, or aforesaid; in the same manner; also.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48:
Ditto \Dit"to\, n.; pl. Dittos. [It., detto, ditto, fr. L.
dictum. See Dictum.]
The aforesaid thing; the same (as before). Often contracted
to do., or to two "turned commas" ("), or small marks. Used
in bills, books of account, tables of names, etc., to save
repetition.
[1913 Webster]
A spacious table in the center, and a variety of
smaller dittos in the corners. --Dickens.
[1913 Webster]